Membrane and associated method

ABSTRACT

Provided is a fluorine substituted oligomeric or polymeric ester including the reaction product of a fluorine substituted acrylate or a fluorine substituted methacrylate; an unsaturated anhydride; and an alkyl acrylate or an alkyl methacrylate. Also provided is a method of making the composition.

BACKGROUND

1. Technical Field

The invention includes embodiments that may relate to a membrane. Theinvention includes embodiments that may relate to method of making themembrane. The invention includes embodiments that may relate to acomposition for use with the membrane.

2. Discussion of Related Art

Membranes with a high porosity, wetability, and chemical resistance maybe useful in, for example, liquid size exclusion filtrationapplications. Polytetrafluoroethylene (PTFE) may be desirable for itschemical resistance, and expanded PTFE (ePTFE) may be desirable for bothchemical resistance and porosity. Z However, due to the hydrophobicproperty of PTFE, liquid water filtration is problematic and may requiretreatment.

Hydrophilicity, and consequently biocompatibility, may be imparted to anePTFE membrane by, for example, impregnation using atetrafluoroethylene/vinyl alcohol copolymer. Such an approach leveragesthe chemical affinity of the perfluoropolymer in the coating material tothe perfluoropolymer of the ePTFE. However, the affinity may besufficiently low that hydrophilicity is of an undesirably shortduration. A porous fluoropolymeric membrane having continuous pores forone side to the other may be rendered hydrophilic by coating themembrane interior with a mixture of a fluoroaliphatic surfactant and ahydrophilic but water insoluble polyurethane. Such an approach mayleverage the chemical affinity between the perfluoropolymers to form atwo-layer system.

In another approach, hydrophilicity of PTFE membrane may be produced byirradiation treatment of the PTFE powdered resin. The resin may beprocessed with a porogen and virgin PTFE powder to render a microporousPTFE membrane.

With reference to the above-disclosed methods, there are commerciallyavailable hydrophilic ePTFE membranes used for liquid water filtration.In addition to the problematic production considerations, thesemembranes may be prewetted by membrane manufacturers and shipped wet toend-users. Such a membrane may dewet (dry). The drying of the membranemay render it ineffective and may present, for example, undesirableshipping considerations. Other undesirable aspects may include economicconsiderations such as handling, shipping weight, and the like.

It may be desirable to have a membrane with properties that differ fromthose properties of currently available membranes. It may be desirableto have a membrane produced by a method that differs from those methodscurrently available.

BRIEF DESCRIPTION

The invention provides, in one embodiment, a membrane including coating.The coating includes a terpolymer having the structure of formula (I)

wherein R1 comprises an alkyl radical; R2 comprises of a formulaCF₃(CF₂)p(CH₂)q- wherein “p” is an integer in a range of from 1 to about21, and “q” is an integer in a range of from 1 to about 10; R3 and R4are separately hydrogen or a short chain alkyl; and “m” is an integergreater than 1, “n” is an integer greater than about 2 to about 20,000,and “o” is an integer greater than about 2.

The invention provides in one embodiment, a membrane include a coating.The coating including the reaction product of a fluorine substitutedacrylate or a fluorine substituted methacrylate; an unsaturatedanhydride; and an alkyl acrylate or an alkyl methacrylate.

The invention provides in one embodiment, a method that includes coatinga membrane with the reaction product of a fluorine substituted acrylateor a fluorine substituted methacrylate; an unsaturated anhydride; analkyl acrylate or an alkyl methacrylate; and an initiator in a solvent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chemical reaction scheme illustrating the use of acomposition for use in a coating in accordance with an embodiment of theinvention.

FIG. 2 is an H-NMR spectrum of a composition in accordance with anembodiment of the invention.

DETAILED DESCRIPTION

The invention includes embodiments that may relate to a membrane coatedwith a composition. The invention includes embodiments that may relateto method of making and/or using the coating composition on themembrane.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about”, is not to be limited to the precise valuespecified. In some instances, the approximating language may correspondto the precision of an instrument for measuring the value. Similarly,“free” may be combined with a term; and, may include an insubstantialnumber, or a trace amount, while still being considered free of themodified term.

A composition according to an embodiment of the invention for use with amembrane may include a terpolymer. Suitable terpolymers may include afluorine substituted oligomeric or polymeric ester. The fluorinesubstituted oligomeric or polymeric ester may include the reactionproduct of a fluorine substituted acrylate or fluorine substitutedmethacrylate; an unsubstituted anhydride; and an alkyl acrylate or alkylmethacrylate.

Suitable fluorine substituted acrylate or fluorine substitutedmethacrylate may have a fluorine substituted aliphatic or aromaticradical. In one embodiment, the fluorine substituted acrylate mayconsist essentially of3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10—heptadecafluorodecyl acrylate. Inone embodiment, the fluorine substituted acrylate may be present in ahamount in a range of greater than about 20 mole percent, or in an amountof about 25 mole percent.

Suitable unsubstituted anhydride may include one or both of itaconicanhydride or maleic anhydride. In one embodiment, the unsubstitutedanhydride consists essentially of itaconic anhydride. In one embodiment,the unsubstituted anhydride consists essentially of maleic anhydride. Inone embodiment, the unsubstituted anhydride may be present in an amountin a range of greater than about 20 mole percent, or in an amount ofabout 25 mole percent.

In one embodiment, the composition may have a structure as defined informula (I):

wherein R1 may include an aliphatic or aromatic radical, R2 may includea fluorine substituted aliphatic or aromatic radical, and R3 and R4 maybe separately either hydrogen or a short chain alkyl, such as methyl.The term “m” may be an integer greater than 1, or in a range of from 1to about 10,000, “n” may be an integer greater than 2, or in a range offrom about 2 to about 20,000, and “o” may be an integer greater than 2,or in a range of from about 2 to about 20,000.

In one embodiment, R2 may be represented by the formula CF₃(CF₂)p(CH₂)q-wherein “p” is an integer greater than 1, or in a range of from 1 toabout 21, and “q” is an integer greater than 1, or in a range of from 1to about 10.

The term polymer may include a reaction product of polymerization; thepolymerization product may include all chemical reaction productscomprising one or more repeated units derived from a reactive substratethat is lower in molecular weight than the reaction product. Examples ofpolymerization products may include one or more of homopolymers,heteropolymers, random copolymers, interpolymers, terpolymers, blockcopolymers, graft copolymers, alternating copolymers, addition polymers,and the like. In one embodiment, the reaction product may be produced byreaction in the presence of an initiator in solution. A suitableinitiator may include an azo-based free radical polymerizationinitiator.

Aliphatic radical or aliphatic moiety, interchangeably, may be anorganic radical having at least one carbon atom, a valence of at leastone and may be a linear array of atoms. Aliphatic radicals may includeheteroatoms such as nitrogen, sulfur, silicon, selenium and oxygen ormay be composed exclusively of carbon and hydrogen. Aliphatic radicalmay include a wide range of functional groups such as alkyl groups,alkenyl groups, alkynyl groups, halo alkyl groups, conjugated dienylgroups, alcohol groups, ether groups, aldehyde groups, ketone groups,carboxylic acid groups, acyl groups (for example, carboxylic acidderivatives such as esters and amides), amine groups, nitro groups andthe like. For example, the 4-methylpent-1-yl radical may be a C₆aliphatic radical comprising a methyl group, the methyl group being afunctional group, which may be an alkyl group. Similarly, the4-nitrobut-1-yl group may be a C₄ aliphatic radical comprising a nitrogroup, the nitro group being a functional group. An aliphatic radicalmay be a haloalkyl group that may include one or more halogen atoms,which may be the same or different. Halogen atoms include, for example;fluorine, chlorine, bromine, and iodine. Aliphatic radicals having oneor more halogen atoms may include the alkyl halides: trifluoromethyl,bromodifluoromethyl, chlorodifluoromethyl, hexafluoroisopropylidene,chloromethyl, difluorovinylidene, trichloromethyl, bromodichloromethyl,bromoethyl, 2-bromotrimethylene (e.g., —CH₂CHBrCH₂—), and the like.Further examples of aliphatic radicals may include allyl, aminocarbonyl(—CONH₂), carbonyl, dicyanoisopropylidene —CH₂C(CN)₂CH₂—), methyl(—CH₃), methylene (—CH₂—), ethyl, ethylene, formyl (—CHO), hexyl,hexamethylene, hydroxymethyl (—CH₂OH), mercaptomethyl (—CH₂SH),methylthio (—SCH₃), methylthiomethyl (—CH₂SCH₃), methoxy,methoxycarbonyl (CH₃OCO—), nitromethyl (—CH₂NO₂), thiocarbonyl,trimethylsilyl ((CH₃)₃Si—), t-butyldimethylsilyl, trimethoxysilylpropyl((CH₃O)₃SiCH₂CH₂CH₂—), vinyl, vinylidene, and the like. By way offurther example, a “₁-C₃₀ aliphatic radical” contains at least one butno more than 30 carbon atoms. A methyl group (CH₃—) may be an example ofa C₁ aliphatic radical. A decyl group (CH₃(CH₂)₉—) may be an example ofa C₁₀ aliphatic radical.

A cycloaliphatic radical or cycloaliphatic moiety, interchangeably, maybe an organic radical having a valence of at least one, and having anarray of atoms, which may be cyclic but which may not be aromatic. Acycloaliphatic radical may include one or more non-cyclic components.For example, a cyclohexylmethyl group (C₆H₁₁CH₂—) may be acycloaliphatic radical, which may include a cyclohexyl ring (the arrayof atoms, which may be cyclic but which may not be aromatic) and amethylene group (the noncyclic component). The cycloaliphatic radicalmay include heteroatoms such as nitrogen, sulfur, selenium, silicon andoxygen, or may be composed exclusively of carbon and hydrogen. Acycloaliphatic radical may include one or more functional groups, suchas alkyl groups, alkenyl groups, alkynyl groups, halo alkyl groups,conjugated dienyl groups, alcohol groups, ether groups, aldehyde groups,ketone groups, carboxylic acid groups, acyl groups (for examplecarboxylic acid derivatives such as esters and amides), amine groups,nitro groups and the like. For example, the 4-methylcyclopent-1-ylradical may be a C₆ cycloaliphatic radical comprising a methyl group,the methyl group being a functional group, which may be an alkyl group.Similarly, the 2-nitrocyclobut-1-yl radical may be a C₄ cycloaliphaticradical comprising a nitro group, the nitro group being a functionalgroup. A cycloaliphatic radical may include one or more halogen atoms,which may be the same or different. Halogen atoms include, for example,fluorine, chlorine, bromine, and iodine. Cycloaliphatic radicals havingone or more halogen atoms may include 2-trifluoro methyl cyclohex-1-yl;4-bromo difluoromethylcyclooct-1-yl; 2-chloro difluoro methylcyclohex-1-yl; hexafluoro isopropylidene-2,2-bis(cyclohex4-yl)(—C₆H₁₀C(CF₃)₂C₆H₁₀—); 2-chloro methyl cyclohex-1-yl; 3-difluoromethylene cyclohex-1-yl; 4-trichloro methyl cyclo hex-1-yloxy; 4-bromodichloro methyl cyclohex-1-yl thio; 2-bromo ethyl cyclo pent-1-yl;2-bromo propyl cyclo hex-1-yloxy (e.g. CH₃CHBrCH₂C₆H₁₀—); and the like.Further examples of cycloaliphatic radicals may include 4-allyloxy cyclohex-1-yl; 4-amino cyclohex-1-yl (H₂NC₆H₁₀—); 4-amino carbonylcyclopent-1-yl (NH₂COC₅H₈—); 4-acetyloxy cyclohex-1-yl; 2,2-dicyanoisopropylidene bis (cyclohex-4-yloxy) (—OC₆H₁₀C(CN)₂C₆H₁₀O—); 3-methylcyclo hex-1-yl; methylene bis (cyclohex 4-yloxy) (—OC₆H₁₀CH₂C₆H₁₀O—);1-ethyl cyclo but-1-yl; cyclo propyl ethenyl; 3-formyl-2-tetrahydrofuranyl; 2-hexyl-5-tetrahydro furanyl; hexamethylene-1,6-bis(cyclohex-4-yloxy) (—O C₆H₁₀(CH₂)₆C₆H₁₀O—); 4-hydroxy methyl cyclohex-1-yl (4-HOCH₂C₆H₁₀—); 4-mercapto methyl cyclo hex-1-yl(4-HSCH₂C₆H₁₀—); 4-methyl thio cyclo hex-1-yl (4-CH₃SC₆H₁₀—); 4-methoxycyclo hex-1-yl; 2-methoxy carbonyl cyclo hex-1-yloxy (2-CH₃OCOC₆H₁₀O—);4-nitro methyl cyclo hex-1-yl (NO₂CH₂C₆H₁₀—); 3-trimethyl silyl cyclohex-1-yl; 2-t-butyl dimethyl silyl cyclo pent-1-yl; 4-trimethoxy silylethyl cyclo hex-1-yl (e.g. (CH₃O)₃SiCH₂CH₂C₆H₁₀—); 4-vinyl cyclohexen-1-yl; vinylidene bis (cyclo hexyl); and the like. The term “aC₃-C₃₀ cycloaliphatic radical” may include cycloaliphatic radicalscontaining at least three but no more than 30 carbon atoms. Thecycloaliphatic radical 2-tetrahydro furanyl (C₄H₇O—) represents a C₄cycloaliphatic radical. The cyclo hexyl methyl radical (C₆H₁₁CH₂—)represents a C₇ cycloaliphatic radical.

An aromatic radical or aromatic moiety, interchangeably, may be an arrayof atoms having a valence of at least one and having at least onearomatic group. This may include heteroatoms such as nitrogen, sulfur,selenium, silicon and oxygen, or may be composed exclusively of carbonand hydrogen. Suitable aromatic radicals may include phenyl, pyridyl,furanyl, thienyl, naphthyl, phenylene, and biphenyl radicals. Thearomatic group may be a cyclic structure having 4n+2 “delocalized”electrons where “n” may be an integer equal to 1 or greater, asillustrated by phenyl groups (n=1), thienyl groups (n=1), furanyl groups(n=1), naphthyl groups (n=2), azulenyl groups (n=2), anthracenyl groups(n=3) and the like. The aromatic radical also may include non-aromaticcomponents. For example, a benzyl group may be an aromatic radical,which may include a phenyl ring (the aromatic group) and a methylenegroup (the non-aromatic component). Similarly a tetrahydro naphthylradical may be an aromatic radical comprising an aromatic group (C₆H₃)fused to a non-aromatic component —CH₂)₄—. An aromatic radical mayinclude one or more functional groups, such as alkyl groups, alkenylgroups, alkynyl groups, haloalkyl groups, haloaromatic groups,conjugated dienyl groups, alcohol groups, ether groups, aldehyde groups,ketone groups, carboxylic acid groups, acyl groups (for examplecarboxylic acid derivatives such as esters and amides), amine groups,nitro groups, and the like. For example, the 4-methylphenyl radical maybe a C₇ aromatic radical comprising a methyl group, the methyl groupbeing a functional group, which may be an alkyl group. Similarly, the2-nitrophenyl group may be a C₆ aromatic radical comprising a nitrogroup, the nitro group being a functional group. Aromatic radicalsinclude halogenated aromatic radicals such as trifluoro methyl phenyl,hexafluoro isopropylidene bis (4-phen-1-yloxy) (—OPhC(CF₃)₂PhO—); chloromethyl phenyl; 3-trifluoro vinyl-2-thienyl; 3-trichloro methyl phen-1-yl(3-CCl₃Ph-); 4-(3-bromo prop-1-yl) phen-1-yl (BrCH₂CH₂CH₂Ph-); and thelike. Further examples of aromatic radicals may include one or more of4-allyloxy phen-1-oxy; 4-amino phen-1-yl (H₂NPh-); 3-amino carbonylphen-1-yl (NH₂COPh-); 4-benzoyl phen-1-yl; dicyano isopropylidene bis(4-phen-1-yloxy) (—OPhC(CN)₂PhO—), 3-methyl phen-1-yl; methylene bis(phen 4-yloxy) (—OPhCH₂PhO—), 2-ethyl phen-1-yl; phenyl ethenyl;3-formyl-2-thienyl; 2-hexyl-5-furanyl; hexamethylene-1,6-bis (phen4-yloxy) (—OPh(CH₂)₆PhO—); 4-hydroxy methylphen-1-yl (4-HOCH₂Ph-);4-mercapto methyl phen-1-yl (4-HSCH₂Ph-); 4-methyl thio phen-1-yl(4-CH₃SPh-); 3-methoxy phen-1-yl; 2-methoxy carbonyl phen-1-yloxy (e.g.,methyl salicyl); 2-nitro methyl phen-1-yl (-PhCH₂NO₂); 3-trimethyl silylphen-1-yl; 4-t-butyl dimethyl silyl phen-1-yl; 4-vinyl phen-1-yl;vinylidene bis (phenyl); and the like. The term “a C₃-C₃₀ aromaticradical” may include aromatic radicals containing at least three but nomore than 30 carbon atoms. A suitable C₃ aromatic radical may include1-imidazolyl (C₃H₂N₂—). The benzyl radical (C₇H₇—) represents a C₇aromatic radical.

FIG. 2 is a graph showing a H-NMR spectrum of a terpolymer according toone embodiment of the invention. A CHCl₃ reference standard is indicatedby reference number 100. A fluorinated carbon chain (—OCH₂—) isindicated by reference number 102; a butyl moiety (—OCH₂—) is indicatedby reference number 104; a portion (—CH₂—) of an itaconic anhydride isindicated by reference number 106; protons in the terpolymer areindicated by the bracket of reference number 108; and a methyl group(—CH₃) of a butyl chain is indicated by reference number 110.

The terpolymer may be further functionalized, grafted, and/orcross-linked. In one embodiment, the terpolymer may be copolymerizedwith a polyether imide, such as the material shown in formula (II).

wherein “s” may be an integer that is equal to or greater than 1.

In one embodiment, the reaction product of the copolymerization may berepresented by the structure as shown by formula (III):

wherein “t” is an integer that may be equal to or greater than 1, “Z”may be an ether or an ester linkage, and “X” may be a hydrogen atom, analkyl group, or a cation.

The anhydride functionality of the terpolymer may be reacted with, forexample, a curing agent. Suitable curing agents may open the anhydridemoiety to cross link. In one embodiment, the anhydride group may crosslink with a corresponding reaction site on the curing agent. Thus, amultifunctional curing agent may react with a plurality of anhydridemoieties from one or more terpolymers to cross link the anhydride moietyand increase the polymer molecular weight.

Suitable curing agents may include free radical initiators, cationicinitiators, anionic initiators, and metal catalysts. Suitable freeradical initiators may include one or more peroxy esters, peroxycarbonates, hydroperoxides, alkylperoxides, arylperoxides, azocompounds, and the like. For cationic and/or anionic polymerization,suitable curing agents may include one or more organic bases, cationiccatalysts, transition metal catalysts, organic acids, and the like canbe employed. Exemplary organic bases may include one or more tertiaryamines (e.g., N,N-dimethyl aniline, N,N-dimethyl toluidine,N,N-dimethyl-p-anisidine, p-halogeno —N,N-dimethyl anilines, 2-N-ethylaniline ethanol, tri-n-butyl amine, pyridine, quinoline, N-methylmorpholine, triethanolamine, or the like); imidazoles; or the like.Organic acids may include phenols (e.g., phenol, cresol, xylenol,resorcinol, phloroglucin, or the like), carboxylic acids, anhydrides, orthe like. Suitable imidazoles may include one or more of isoimidazole,2-methyl imidazole, 2-ethyl-4-methylimidazole, 2,4-dimethylimidazole,butylimidazole, 2-heptadecenyl 4-methylimidazole, 2-undecenylimidazole,1-vinyl-2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole,1-benzyl-2-methylimidazole, 1-propyl -2-methylimidazole,1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole,1-cyanoethyl-2-undecylimidazole,1-cyanoethyl-1-guanaminoethyl-2-methylimidazole,2-n-heptadecyl-4-methylimidazole, phenylimidazol, benzylimidazole,2-methyl 4,5-diphenylimidazole, 2,3,5-triphenylimidazole,2-styrylimidazole, 1-(dodecyl benzyl)-2-methylimidazole,2-(2-hydroxyl-4-t-butylphenyl)-4,5-diphenylimidazole,2-(2-methoxyphenyl)-4,5-diphenylimidazole,2-(3-hydroxyphenyl)-4,5-diphenylimidazole, 2-(p-dimethylaminophenyl)-4,5-diphenylimidazole,2-(2-hydroxyphenyl)-4,5-diphenylimidazole,di(4,5-diphenyl-2-imidazole)benzene-1,4,2-naphthyl-4,5-diphenylimidazole,1-benzyl-2-methylimidazole, 2-p-methoxystyrylimidazole, or 2-phenyl4,5-dihydroxymethylimidazole. In one embodiment, a suitable imidizolederivative may include trimellitic acid. Suitable other organic acidsand organic bases are discussed further hereinbelow.

Exemplary cationic catalysts may include one or more onium salts,iodonium salts, sulfonium salts, or the like. Exemplary metal catalystsmay include titanium, zirconium, hafnium, lead, zinc, tin, manganese,nickel, copper, cobalt or the like. Suitable metal catalysts may be inthe form of a chelate, a soap, or the like. Examples of such metalcatalyst compounds may include metallocenes of titanium, zirconium, orhafnium, lead naphthenate, lead stearate, zinc naphthenate, tin oleate,dibutyl tin maleate, manganese naphthenate, cobalt naphthenate, leadsalt of resin acid, or metal chlorides (such as ZnCl₂, SnCl₄ or AlCl₃),or the like.

Other suitable curing agents may include carboxylic acids, such asaliphatic dicarboxylic acids, cycloaliphatic dicarboxylic acids, andaromatic dicarboxylic acids. The molecular weight of the dicarboxylicacid may be less than about 300, in a range of from about 300 to about500, from about 500 to about 1000, or greater than about 1000. As usedherein, the term ‘carboxylic acids’ includes carboxylic acids, andequivalents of carboxylic acids, having two or more functional carboxylgroups, or groups which perform like carboxylic acids in reaction withglycols and diols in forming polyesters. These equivalents may includeesters and ester-forming reactive derivatives, such as acid halides andanhydrides. The molecular weight preference mentioned above pertains tothe acid rather than the equivalent ester or ester-forming derivatives.

Aliphatic dicarboxylic acids refer to carboxylic acids having twocarboxyl groups each of which is attached to a saturated carbon atom. Ifthe carbon atom to which the carboxyl group is attached is saturated andis in a ring, the acid is cycloaliphatic. Aromatic dicarboxylic acidsrefer to dicarboxylic acids having two carboxyl groups each of which isattached to a carbon atom in an isolated or fused benzene ring system.It is not necessary that both functional carboxyl groups be attached tothe same aromatic ring.

Other suitable curing agents may include aliphatic acids andcycloaliphatic acids. In one embodiment, aliphatic acids andcycloaliphatic acids may include one or more of sebacic acid,1,2-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid,adipic acid, glutaric acid, succinic acid, oxalic acid, dimer acid,4-cyclohexene-1,2-dicarboxylic acid, 2-ethysuberic acid,tetramethylsuccinic acid, cyclopentanedicarboxylic acid, decahydro-1,5naphthalene dicarboxylic acid, 4,4′-bicyclohexyl dicarboxylic acid,decahydro-2,6 naphthalene dicarboxylic acid, 4,4methylenebis(cyclohexane carboxylic acid), 3,4-furan dicarboxylic acid,or 1,1-cyclobutane dicarboxylic acid.

Suitable aromatic dicarboxylic acids may include one or more ofterephthalic acid; phthalic acid; isophthalic acid; bi-benzoic acid; bis(p-carboxyphenyl)methane; oxybis benzoic acid; ethylene-1,2-bisp-oxybenzoic acid; 1,5-naphthalene dicarboxylic acid; 2,6-naphthalenedicarboxylic acid; 2,7-naphthalene dicarboxylic acid; phenanthrenedicarboxylic acid; anthracene dicarboxylic acid; 4,4′-sulfonyl dibenzoicacid; and halo and C1-C12 alkyl, alkoxy, and aryl ring substitutionderivatives thereof. Hydroxy acids such as p (beta-hydroxy ethoxy)benzoic acid may be used in conjunction with an aromatic dicarboxylicacid.

Suitable curing agents may include polyfunctional amines, such asdiamines. In one embodiment, the diamine may include one or both of2,2′-(ethylene dioxy)diethylamine or hexamethylene diamine. In oneembodiment, the diamine may include one or more ofN,N′-bis-(2-butyl)-p-methylene dianiline; N,N′-bis4-(5-methyl-2-butyl)-p-phenylene diamine;N,N′-bis-4-(2-butyl)-p-phenylene diamine;N-2-pentyl-N′-phenyl-p-phenylene diamine, or N,N′-bis4-(2-methylpropyl)-o-phenylene diamine.

Other suitable polyfunctional amines may include one or more of4,4′-diamino diphenylmethane; o-, m-, or p-phenylene diamine; bis(4-(3-amino phenoxy)phenyl)sulfone; 2,4-diamino toluene; 2,5-diaminotoluene; 2,4-diamino xylene; 2,4-diamino durene; dialkyl 4,4′-diaminodiphenyls, such as dimethyl-4,4′-diamino diphenyl; dialkoxy 4,4′-diaminodiphenyl, such as dimethoxy-4,4′-diamino diphenyl or diethoxy4,4′-diamino diphenyl; 4,4′-diamino diphenyl ether; 3,4′-diaminodiphenyl ether; 4,4′-diamino diphenyl sulfone; 3,3′-diamino diphenylsulfone; 4,4′-diamino benzophenone; 3,3′-diamino benzophenone;1,3-bis(3-amino phenoxy) benzene; 1,3-bis(4-amino phenoxy)benzene;1,4-bis(4-amino phenoxy)benzene; 4,4′-bis(4-amino phenoxy)biphenyl;bis(4-(4-amino phenoxy) phenyl)sulfone; 2,2′-bis(4-(4-aminophenoxy)phenyl)propane; 2,2-bis(4-(4-amino phenoxy)phenyl)hexafluoropropane; 2,2-bis(4-(3-amino phenoxy)phenyl)propane; 2,2-bis(4-(3-aminophenoxy)phenyl)hexafluoro propane; 2,2-bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)hexafluoro propane; 2,2-bis(4-(3-amino-5-trifluoromethylphenoxy)phenyl)hexafluoro propane; 2,2-bis(4-aminophenyl)hexafluoro propane; 2,2-bis(3-amino phenyl)hexafluoro propane;2,2-bis(3-amino-4-hydroxyphenyl)hexafluoro propane;2,2-bis(3-amino-4-methylphenyl)hexafluoro propane; 4,4′-bis(4-aminophenoxy)octafluoro biphenyl; 2,2′-bis(trifluoro methyl)diamino diphenyl;3,5-diamino benzotrifluoride; 2,5-diamino benzo trifluoride; 3,3′-bistrifluoro methyl-4,4′-diamino biphenyl; 3,3′-bis trifluoromethyl-5,5′-diamino biphenyl; bis(trifluoro methyl)-4,4′-diaminodiphenyl; bis(fluorinated alkyl)-4,4′-diamino diphenyls;dichloro-4,4′-diamino diphenyl; dibromo-4,4′-diamino diphenyl;bis(fluorinated alkoxy)-4,4′-diamino diphenyls; diphenyl 4,4′-diaminodiphenyl; 4,4′-bis(4-amino tetrafluoro phenoxy)tetrafluoro benzene;4,4′-bis(4-amino tetrafluoro phenoxy)octafluoro biphenyl;4,4′-binaphthyl amine; 4,4′-diamino benzanilide; or4,4′-diamino(N-alkyl)benzanilides. Other suitable polyfunctional aminesmay include one or more aminosiloxane or aminosilane, such as1,3-bis(3-amino propyl)-1,1,2,2-tetramethyl disiloxane, 1,3-bis(3-aminobutyl)-1,1,2,2-tetramethyl disiloxane, bis(4-aminophenoxy)dimethylsilane, or 1,3-bis(4-amino phenoxy) tetramethyldisiloxane. In one embodiment, the polyfunctional curing agent mayinclude a polyfunctional azo compound. In one embodiment, the curingagent may consist essentially of 2,2′-(ethylene dioxy)diethylamine. Inone embodiment, the curing agent may consist essentially ofhexamethylene diamine.

An otherwise hydrophobic sheet may be rendered relatively morehydrophilic by a treatment with a composition according to an embodimentof the invention. The sheet may be porous, and as such may be referredto as a base membrane. As used herein, a base membrane may refer to anuncoated membrane, while the more general term of membrane may refer toa membrane that comprises an embodiment of the invention, unlesslanguage or context indicates otherwise.

The base membrane may be rendered permeable by one or more ofperforating, stretching, expanding, bubbling, or extracting the basemembrane, for example. Suitable methods of making the membrane also mayinclude foaming, skiving or casting any of the suitable materials. Inalternate embodiments, the membrane may be formed from woven ornon-woven fibers.

In one embodiment, continuous pores may be produced. Suitable porositymay be in a range of greater than about 10 percent. In one embodiment,the porosity may be in a range of from about 10 percent to about 20percent, from about 20 percent to about 30 percent, from about 30percent to about 40 percent, from about 40 percent to about 50 percent,from about 50 percent to about 60 percent, from about 60 percent toabout 70 percent, from about 70 percent to about 80 percent, from about80 percent to about 90 percent, or greater than about 90 percent. Hereand throughout the specification and claims, range limitations may becombined and/or interchanged, such ranges are identified and include allthe sub-ranges contained therein unless context or language indicatesotherwise.

Pore diameter may be uniform, or may be in a predetermined pattern.Suitable pore diameters may be less than about 50 micrometers. In oneembodiment, an average pore diameter may be in a range of from about 50micrometers to about 40 micrometers, from about 40 micrometers to about30 micrometers, from about 30 micrometers to about 20 micrometers, fromabout 20 micrometers to about 10 micrometers, from about 10 micrometersto about 1 micrometer. In one embodiment, the average pore diameter maybe less than about 1 micrometer, in a range of from about 1 micrometerto about 0.5 micrometers, from about 0.5 micrometers to about 0.25micrometers, from about 0.25 micrometers to about 0.1 micrometers, orless than about 0.1 micrometers. In one embodiment, the average porediameter may be in a range of from about 0.1 micrometers to about 0.01micrometers.

In one embodiment, the base membrane may be a three-dimensional matrixor have a lattice type structure including plurality of nodesinterconnected by a plurality of fibrils. Surfaces of the nodes andfibrils may define a plurality of pores in the membrane. The size of afibril that has been at least partially sintered may be in a range offrom about 0.05 micrometers to about 0.5 micrometers in diameter takenin a direction normal to the longitudinal extent of the fibril. Thespecific surface area of the porous membrane may be in a range of fromabout 9 square meters per gram of membrane material to about 110 squaremeters per gram of membrane material.

Surfaces of nodes and fibrils may define numerous interconnecting poresthat extend through the membrane between opposite major side surfaces ina tortuous path. In one embodiment, the average effective pore size ofpores in the membrane may be in the micrometer range. A suitable averageeffective pore size for pores in the membrane may be in a range of fromabout 0.01 micrometers to about 0.1 micrometers, from about 0.1micrometers to about 5 microns, from about 5 micrometers to about 10micrometers, or greater than about 10 micrometers.

In one embodiment, the base membrane may be made by extruding a mixtureof fine powder particles and lubricant. The extrudate subsequently maybe calendered. The calendered extrudate may be “expanded” or stretchedin one or more directions, to form fibrils connecting nodes to define athree-dimensional matrix or lattice type of structure. “Expanded” meansstretched beyond the elastic limit of the material to introducepermanent set or elongation to fibrils. The membrane may be heated or“sintered” to reduce and minimize residual stress in the membranematerial by changing portions of the material from a crystalline stateto an amorphous state. In one embodiment, the membrane may be unsinteredor partially sintered as is appropriate for the contemplated end use ofthe membrane.

In one embodiment, the base membrane may define many interconnectedpores that fluidly communicate with environments adjacent to theopposite facing major sides of the membrane. The propensity of thematerial of the membrane to permit a liquid material, for example, anaqueous liquid material, to wet out and pass through pores may beexpressed as a function of one or more properties. The properties mayinclude the surface energy of the membrane, the surface tension of theliquid material, the relative contact angle between the material of themembrane and the liquid material, the size or effective flow area ofpores, and the compatibility of the material of the membrane and theliquid material.

Membranes according to embodiments of the invention may have differingdimensions, some selected with reference to application-specificcriteria. In one embodiment, the membrane may have a thickness in thedirection of fluid flow in a range of less than about 10 micrometers. Inanother embodiment, the membrane may have a thickness in the directionof fluid flow in a range of greater than about 10 micrometers, forexample, in a range of from about 10 micrometers to about 100micrometers, from about 100 micrometers to about 1 millimeter, fromabout 1 millimeter to about 5 millimeters, or greater than about 5millimeters.

Perpendicular to the direction of fluid flow, the membrane may have awidth of greater than about 10 millimeters. In one embodiment, themembrane may have a width in a range of from about 10 millimeters toabout 45 millimeters, from about 45 millimeters to about 50 millimeters,from about 50 millimeters to about 10 centimeters, from about 10centimeters to about 100 centimeters, from about 100 centimeters toabout 500 centimeters, from about 500 centimeters to about 1 meter, orgreater than about 1 meter. The width may be a diameter of a circulararea, or may be the distance to the nearest peripheral edge of apolygonal area. In one embodiment, the membrane may be rectangular,having a width in the meter range and an indeterminate length. That is,the membrane may be formed into a roll with the length determined bycutting the membrane at predetermined distances during a continuousformation operation.

In one embodiment, the coating forms a layer having an average thicknessin a range of from about 1 nanometer to about 500 nanometers, from about500 nanometers to about 1 micrometer, or greater than about 1micrometer. The coating layer may be uniform in thickness, or may have athickness that differs from area to area.

A membrane prepared according to embodiments of the invention may haveone or more predetermined properties. Such properties may include one ormore of a wetability of a dry-shipped membrane, a wet/dry cyclingability, filtering of polar liquid or solution, flow of non-aqueousliquid or solution, flow and/or permanence under low pH conditions, flowand/or permanence under high pH conditions, flow and/or permanence atroom temperature conditions, flow and/or permanence at elevatedtemperature conditions, flow and/or permanence at elevated pressures,transparency to energy of predetermined wavelengths, transparency toacoustic energy, or support for catalytic material. Permanence refers tothe ability of the coating material to maintain function in a continuingmanner, for example, for more than 1 day or more than one cycle(wet/dry, hot/cold, high/low pH, and the like).

A property of at least one embodiment may include a resistance totemperature excursions in a range of from about 100 degrees Celsius toabout 125 degrees Celsius, for example, in autoclaving operations.Optionally, the temperature excursion may be at an elevated pressurerelative ambient. In one embodiment, resistance to ultraviolet (UV)radiation may allow for sterilization of the membrane without loss ofproperties. Of note is an alternative embodiment in which cross-linkingof the coating composition may be initiated or facilitated by exposureto an irradiation source, such as a UV source, where UV initiators maycompete with UV absorbing compositions, if present.

Flow rate of fluid through the membrane may be dependent on one or morefactors. The factors may include one or more of the physical and/orchemical properties of the membrane, the properties of the fluid (e.g.,viscosity, pH, solute, and the like), environmental properties (e.g.,temperature, pressure, and the like), and the like. In one embodiment,the membrane may be permeable to vapor rather than, or in addition to,fluid or liquid. A suitable vapor transmission rate, where present, maybe in a range of less than about 1000 grams per square meter per day(g/m²/day), from about 1000 g/m²/day to about 1500 g/m²/day, from about1500 g/m²/day to about 2000 g/m²/day, or greater than about 2000g/m²/day. In one embodiment, the membrane may be selectively impermeableto vapor, while remaining permeable to liquid or fluid.

The membrane may be used to filter water. In one embodiment, the watermay flow through the membrane at flow rate that is greater than about 5mL/min-cm at a pressure differential of 27 inches Hg at room temperatureafter 10 wet/dry cycles. In one embodiment, the water may flow throughthe membrane at flow rate that is greater than about 5 mL/min-cm at apressure differential of 27 inches Hg at about 100 degrees Celsius after10 wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 10 mL/min-cm at apressure differential of 27 inches Hg at room temperature after 10wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 10 mL/min-cm at apressure differential of 27 inches Hg at 100 degrees Celsius after 10wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 20 mL/min-cm at apressure differential of 27 inches Hg at room temperature after 10wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 20 mL/min-cm at apressure differential of 27 inches Hg at about 100 degrees Celsius after10 wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 5 mL/min-cm at apressure differential of 27 inches Hg at room temperature after 20wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 5 mL/min-cm at apressure differential of 27 inches Hg at 100 degrees Celsius after 20wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 10 mL/min-cm at apressure differential of 27 inches Hg at room temperature after 20wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 10 mL/min-cm at apressure differential of 27 inches Hg at 100 degrees Celsius after 20wet/dry cycles. In one embodiment, the water may flow through themembrane at flow rate that is greater than about 20 mL/min-cm at apressure differential of 27 inches Hg at room temperature after 50wet/dry cycles.

In one embodiment, the membrane may be absorbent, such as water orbodily fluid absorbent. Absorbent may include insignificant amounts offluid influx and outflow when maintaining equilibrium with a fluidicenvironment. However, absorbent is distinguishable, and distinguishedfrom, flowable. Flow includes an ability of liquid or fluid to flow froma first surface through the membrane and out a second surface. Thus, inone embodiment, the membrane may be operable to have a liquid or fluidflow through at least a portion of the material in a predetermineddirection. The motive force may be osmotic or wicking, or may be drivenby one or more of a concentration gradient, pressure gradient,temperature gradient, or the like.

The membrane may have a plurality of sub layers. The sub layers may bethe same as, or different from, each other. In one aspect, one or moresub layer may include an embodiment of the invention, while another sublayer may provide a property such as, for example, reinforcement,selective filtering, flexibility, support, flow control, and the like.

A membrane according to embodiments of the invention may be used as, forexample, a proton exchange membrane (PEM) in a fuel cell. Other suitableapplications may include liquid filtration, polarity-based chemicalseparations, electrolysis, batteries, pervaporization, gas separation,dialysis separation, industrial electrochemistry such as chloralkaliproduction and electrochemical applications, super acid catalysts, oruse as a medium in enzyme immobilization.

In one embodiment, a hydrophilic porous expanded polytetrafluoroethylene(ePTFE) membrane may be prepared by treating a virgin ePTFE membranewith a hydrophilic precursor acrylate terpolymer. After the treatment,the terpolymer may be cross-linked using a diamine. Such cross-linkingmay mechanically interlock the coating onto fibrils and nodes of theePTFE porous network. During cross-linking, the hydrophilicity of thehydrophilic precursor acrylate terpolymer may be activated by a reactionbetween itaconic anhydride units on the terpolymer backbone with thecuring agent, such as a diamine. The activation may include generatingcarboxylic acid groups and inter- and intra-molecular ion pairs.Consequently, the coated ePTFE membrane may be rendered liquid waterwetability. The wetability of this coated ePTFE membrane may be retainedduring wet/dry cycling of the membrane.

EXAMPLES

The following examples only illustrate methods and embodiments inaccordance with the invention, and do not impose limitations upon theclaims. Unless specified otherwise, all ingredients are commerciallyavailable from such common chemical suppliers as Alpha Aesar, Inc. (WardHill, Mass.), Sigma-Aldrich Company (St. Louis, Mo.), and the like.

Example 1 Preparation of Terpolymer Composition

A solution of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecylacrylate (4.043 grams (g), 7.8 millimoles (mmol)), itaconic anhydride(0.875 g; 7.8 mmol), butyl acrylate (2 g; 15.6 mmol),2,2′-azobis(2-methylpropionitrile) (AIBN) (0.0138 g, 0.08 mmol), andtetrahydrofuran (10 g, 138.7 mmol) are placed in a 250 milliliter (mL)Chemglass Airfree tube. The solution is degassed by freeze-pump-thaw (3cycles) under nitrogen. The degassed solution is polymerized at 60degrees Celsius for 24 hours (h). The reaction product is cooled to roomtemperature and precipitated from heptane (150 mL) under vigorousstirring.

The reaction product is a terpolymer that may have a molar ratio of a=1,b=2, and z=2 assembled in a random orientation, and an average molecularweight (Mw) in a range of from about 5,000 to about 200,000. A schematicof the reaction scheme is illustrated below. The terpolymer is solublein a moderately polar solvent such as as acetone, but is relativelyinsoluble in a polar-protic solvent, such as methanol. Unreacteditaconic anhydride is soluble in both acetone and methanol. Afterprecipitation in a non-polar solvent, a polar solvent wash allows forrecovery of the terpolymer without unreacted anhydride.

Example 2 Preparation of Terpolymer Composition

A solution of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecylacrylate (4.043 grams (g), 7.8 millimoles (mmol)), itaconic anhydride(1.747 g; 15.6 mmol), butyl acrylate (1 g; 7.8 mmol),2,2′-azobis(2-methylpropionitrile) (AIBN) (0.0136 g, 0.08 mmol), andtetrahydrofuran (13.3 mL, 184.4 mmol) are placed in a 250 milliliter(mL) Chemglass Airfree tube. The solution is degassed byfreeze-pump-thaw (3 cycles) under nitrogen. The degassed solution ispolymerized at 60 degrees Celsius for 24 hours (h). The reaction productis cooled to room temperature and precipitated from heptane (150 mL)under vigorous stirring. H-NMR analysis indicates that a relativelylarge yield of the isolated composition is itaconic anhydride with aportion of terpolymer present. The precipitate is dissolved in acetoneand reprecipitated from methanol to afford a white powder.

Analysis indicates that the terpolymer is a major component of thesecond precipitated product. The itaconic anhydride remains in themethanol/acetone solution.

Example 3 Preparation of Terpolymer Composition

A solution of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecylacrylate (4.043 grams (g), 7.8 millimoles (mmol)), itaconic anhydride(1.75 g; 15.6 mmol), butyl acrylate (2 g; 15.6 mmol),2,2′-azobis(2-methylpropionitrile) (AIBN) (0.0068 g, 0.08 mmol), andtetrahydrofuran (17.8 g, 246.8 mmol) are placed in a 250 milliliter (mL)Chemglass Airfree tube. The solution is degassed by freeze-pump-thaw (3cycles) under nitrogen. The degassed solution is polymerized at 60degrees Celsius for 24 hours (h). The reaction product is cooled to roomtemperature and precipitated from heptane (150 mL) under vigorousstirring. H-NMR analysis indicates that a relatively large yield of theisolated composition is itaconic anhydride with a portion of terpolymerpresent. The precipitate is dissolved in acetone and reprecipitated frommethanol to afford a white powder.

Analysis indicates that the second precipitated product is largely theterpolymer. The itaconic anhydride remains in the methanol/acetonesolution. The yield amount indicates that varying the relativeproportions of starting ingredients impacts yield. Further, smallchanges in the proportions have a large impact on yield. Another methodof reducing the level of unreacted itaconic anhydride is to use avariable feed rate to introduce the corresponding monomer into thereaction, rather than a one pot process.

Example 4 Treatment of Membrane

Eight virgin expanded polytetrafluoroethylene (ePTFE) membranes aretreated with the solution from Example 1 and a curing agent solution.The curing agent solution includes 2,2′-(ethylenedioxy) diethylamine andhexamethylenediamine. The curing agent is added in an amount sufficientto have a 1:1 stoichiometrically balanced ratio based on functionalityrelative to the anhydride moiety. The coated membranes are heated tocross-link the terpolymer from Example 1, and to form an interlockingcoating on the treated membrane.

Under observation, the treated membranes samples readily wet out whencontacted with liquid water. The initial water flow rate is evaluated.Four of the samples are subjected to five wet/dry cycles using water at22 degrees Celsius. The samples all continued to flow water therethrough after the cycling.

Another four of the samples are subjected to wet/dry cycles using waterat 100 degrees Celsius. The samples continue to flow water there throughafter at least 3 hot water wet/dry test cycles at 1 liter per cycle.Various subsequent flow rates are observed. The flow rates range from 1mL/min-cm² to 23 mL/min-cm² at 27 Hg pressure differential.

The embodiments described herein are examples of compositions,structures, systems and methods having elements corresponding to theelements of the invention recited in the claims. This writtendescription may enable those of ordinary skill in the art to make anduse embodiments having alternative elements that likewise correspond tothe elements of the invention recited in the claims. The scope of theinvention thus includes compositions, structures, systems and methodsthat do not differ from the literal language of the claims, and furtherincludes other structures, systems and methods with insubstantialdifferences from the literal language of the claims. While only certainfeatures and embodiments have been illustrated and described herein,many modifications and changes may occur to one of ordinary skill in therelevant art. The appended claims cover all such modifications andchanges.

1. A membrane comprising a coating, the coating comprising: a terpolymerhaving the structure of formula (I)

wherein R1 comprises an alkyl radical; R2 comprises of a formulaCF₃(CF₂)p(CH₂)q- wherein “p” is an integer in a range of from 1 to about21, and “q” is an integer in a range of from 1 to about 10; R3 and R4are separately hydrogen or a short chain alkyl; and “m” is an integergreater than 1, “n” is an integer greater than about 2 to about 20,000,and “o” is an integer greater than about
 2. 2. The membrane as definedin claim 1, wherein R1 is an alkyl radical having from C1 to about C10carbon atoms.
 3. The membrane as defined in claim 2, wherein R1 isbutyl.
 4. The membrane as defined in claim 1, wherein R2 is fullysubstituted with fluorine.
 5. The membrane as defined in claim 1,wherein R2 is an alkyl radical having from C1 to about C10 carbon atoms.6. The membrane as defined in claim 5, wherein R2 is an alkyl chainhaving more than about C5 carbon atoms.
 7. The membrane as defined inclaim 1, wherein R2 is a linear chain.
 8. The membrane as defined inclaim 1, wherein “m”, “n”, and “o” represent mole proportions of 1:2:2respectively.
 9. The membrane as defined in claim 1, wherein the coatingfurther comprises a curing agent.
 10. The membrane as defined in claim9, wherein the coating is cross-linked to form a hydrophilic coatedmembrane.
 11. The membrane as defined in claim 10, wherein the coatedmembrane is re-wettable in the absence of alcohol after at least onewet/dry cycle.
 12. The membrane as defined in claim 10, wherein thecoated membrane has a flow rate of water that is greater than about 1mL/min-cm at 27 inches Hg pressure differential after 10 wet/dry cyclesat room temperature.
 13. The membrane as defined in claim 1, wherein themembrane comprises one or both of polyvinylidene fluoride orpolytetrafluoroethylene.
 14. The membrane as defined in claim 1, whereinthe base membrane comprises one or more of polyethylene, polyolefin,polyamide, polyester, polysulfone, polyether, polyacrylic,polymethacrylic, polystyrene, polyurethane, polypropylene, polyphenelenesulfone, polyphenylene oxide, or cellulosic polymer.
 15. A membranecomprising a coating, wherein the coating comprises a reaction productof: a fluorine substituted acrylate or a fluorine substitutedmethacrylate; an unsaturated anhydride; and an alkyl acrylate or analkyl methacrylate.
 16. The membrane as defined in claim 15, wherein theunsaturated anhydride comprises itaconic anhydride or maleic anhydride.17. The membrane as defined in claim 16, wherein the itaconic anhydrideis present in an amount in a range of greater than about 20 molepercent.
 18. The membrane as defined in claim 20, wherein the itaconicanhydride is present in an amount of about 25 mole percent.
 19. Themembrane as defined in claim 15, wherein the fluorine substitutedacrylate comprises3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl acrylate. 20.The membrane as defined in claim 15, wherein the fluorine substitutedacrylate is present in an amount in a range of greater than about 20mole percent.
 21. The membrane as defined in claim 20, wherein thefluorine substituted acrylate is present in an amount of about 25 molepercent.
 22. The membrane as defined in claim 15, wherein the alkylacrylate is present in an amount in a range of greater than about 35mole percent.
 23. The membrane as defined in claim 22, wherein the alkylacrylate is present in an amount of about 50 mole percent.
 24. Themembrane as defined in claim 15, wherein the alkyl acrylate comprisesbutyl acrylate.
 25. The membrane as defined in claim 15, furthercomprising residual amounts of an azo-based free radical polymerizationinitiator.
 26. The membrane as defined in claim 15, wherein the coatingfurther comprises a polyfunctional cross-linking agent.
 27. The membraneas defined in claim 26, wherein the cross-linking agent comprises apolyfunctional amine.
 28. The membrane as defined in claim 27, whereinthe polyfunctional amine comprises one or both of 2,2′-(ethylenedioxy)diethylamine or hexamethylenediamine.
 29. The membrane as defined inclaim 28, wherein: the fluorine substituted acrylate consistsessentially of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecylacrylate; the unsaturated anhydride consists essentially of itaconicanhydride; and the alkyl acrylate consists essentially of butylacrylate.
 30. The membrane as defined in claim 26, wherein the coatingis cross-linked with the polyfunctional cross-linking agent to form acoated membrane.
 31. The membrane as defined in claim 30, wherein thecoated membrane has a flow rate of water that is greater than about 1mL/min-cm at 27 inches Hg pressure differential after 10 wet/dry cyclesat room temperature.
 32. A method, comprising: reacting a fluorinesubstituted acrylate or a fluorine substituted methacrylate; anunsaturated anhydride; an alkyl acrylate or an alkyl methacrylate; andan initiator in a solvent to form a terpolymer; and reacting theterpolymer and a polyfunctional cross-linking agent to form a coating ona membrane.
 33. The method as defined in claim 32, further comprisingwherein the cross-linking agent comprises one or both of2,2′-(ethylenedioxy)diethylamine or hexamethylenediamine.
 34. The methodas defined in claim 32, wherein reacting comprises curing the terpolymerto form a cross-linked hydrophilic coating.
 35. The method as defined inclaim 34, wherein curing comprises generating a network of hydrophilicfunctionality such as carboxylic acid groups and inter/intramolecularammonium-carboxylate ion pairs to impart hydrophilicity.
 36. The methodas defined in claim 32, further comprising flowing water through themembrane.